The invention pertains to printers, and more particularly to the construction of a printer particularly suited for POS/ECR applications.
Conventional printers for printing on slips, which is one type of cut sheet, must generally have a flat recording sheet guide of large area because slips comes in various sizes and may contain many printing lines. Few such printers (generally called "slip printers") allow the use of a rolled sheet.
A validation sheet, which also is a type of cut sheet, is generally available in a regular size. However, validation sheets are multiple-layer sheets, that is, each validation sheet includes plural copying sheets behind the front or top sheet. Conventional printers dedicated to rolled sheet printing, on the other hand, have not been able to accommodate validation sheets along their recording sheet paths.
FIG. 11 is a schematic diagram showing a slip printer designed for slip printing, in which reference numeral 401 designates a print head; 12, a slip sheet, which is a recording sheet; 404 and 405, sheet forwarding rollers for forwarding the slip sheet 12 while interposing it therebetween; 403, a positioning member for positioning the slip sheet before starting to print; and 402a and 402b, a pair of recording sheet detectors. As shown in FIG. 11, it is common to provide two detectors, one 402a for detecting the head end of the slip sheet 12, and the other 402b for detecting its tail end to inform of a print limit.
FIG. 12 is a schematic diagram showing a printer designed for validation sheet printing, in which reference numeral 13 designates a validation sheet; and 406, a sheet guide and positioning member. As shown in FIG. 12, this printer is provided with a recording sheet detector 402c for detecting the tail end of the validation sheet 13.
In FIGS. 13 and 14 are block diagrams of a conventional recording sheet control system. With this system, the means for forwarding the continuous sheets such as journal sheets and receipts the means for forwarding cut sheets such as slips are driven by separate drive sources and separate clutch means 411 and 412. Some conventional systems control a single drive source by switching the drive force using drive force switching means 413 between cut sheet printing and rolled sheet printing.
Recently, POS/ECR printers capable of handling various types of recording sheets used in POS markets have been called for. However, an attempt to integrate the conventional slip printer and validation printer, and even a rolled sheet printer, together into a POS/ECR printer requires that a printing section be provided separately for each type of printing operation or a number of recording sheet detectors be employed, thereby making such a printer not only expensive but also large in structure.
In addition, ordinary validation sheets, which are thick since a number of copying sheets are attached, are susceptible to separation and jamming as they pass along the long recording sheet forwarding path, which is troublesome.
Moreover, the conventional recording sheet forwarding paths, each driven by a separate drive source and a separate clutch, require an expensive and complicated control system involving a large number of parts. A single drive system such as shown in FIG. 14 employs a gear switching mechanism as the drive force switching means. However, to meet the latest demand no only for independent operation of both slip printing and rolled sheet printing but also for their simultaneous operation in which the slip printing content is simultaneously printed on a rolled sheet as a journal for security purposes (hereinafter referred to as "security slip"), the conventional printer does not provide the necessary functions.